         (get-css-hour-minute-classes-for-time startTime)]
     ; Create new row if necessary
     (if (= rowNum (get-nr-rows-in-timetable-day day))
-        (add-new-row-to-timetable-day day))
+        (add-new-row-to-timetable-day! day))
 
     ; Update in-memory representation of timetable
     (timetable-add-lesson day

    [(str "h" (if (< hour 10) "0" "") hour)
     (str "m" (if (not= minute 0) "30" "00"))]))

(defn- add-module-lesson
  "Adds a single lesson of a module (obtained from the `ModulesMap` global) to
   the timetable, and returns its jQuery div element."
  [moduleCode moduleName lessonType lessonLabel modulesMapLesson bgColorCssClass

   <td class='h23 m00'></td>
   <td class='h23 m30'></td>")

(defn- add-new-row-to-timetable-day!
  "Adds a new row to the 0-indexed day in the Timetable, where 0 = Monday,
   1 = Tuesday, until 4 = Friday."
  [day]
